This invention relates to a new catalyst material, to methods of preparing the same, and to methods and apparatus using it. In one of its preferred forms, the invention relates to new catalyst materials suitable for promoting chemical reactions, especially such reactions for which platinum has previously been used as the catalyst.
Catalyst materials are known in the prior art which affect certain chemical reactions in a desired way without themselves being used up or substantially modified during the process. Among the primary desirable attributes of such a catalyst are high catalytic activity at an appropriate temperature, relatively low cost, easy availability and plentiful supply. Heretofore platinum has been considered the best catalyst material for many purposes from the viewpoint of catalytic activity, but it is very expensive and in limited supply. Furthermore, even greater catalytic activity than is provided by platinum would, of course, also be desirable. Among the many applications in which such catalysts are useful are in catalytic cracking processes, as the catalyst at one or more of the electrodes in a fuel cell, as a catalyst for facilitating the synthesizing of various chemical compounds, as the catalyst for facilitating certain general types of oxidizing and/or reducing chemical reactions, and as a catalyst for promoting certain purifying or pollution-reducing chemical reactions, for example in converting the pollutive substances in engine exhausts to less harmful materials.
In the auto exhaust field the need and the search for an effective yet inexpensive catalyst have been particularly intense. Government specifications for permissive levels of emission of carbon monoxide and oxides of nitrogen will require the use of emission-reducing equipment in automobiles, and to the present time it appears that even though such equipment is used the design and/or adjustment of automobile engines will nevertheless have to be modified in a manner to reduce engine-efficiency and power. Accordingly, an effective and inexpensive exhaust catalyzer is desirable not only to reduce the size and cost of the catalyzer but also to widen the permissible range of engine designs and adjustments.
There is a wide variety of substances and combinations of substances which have been proposed for use as catalysts, primarily in an effort to avoid the excessive costs of platinum, and while such are usable for certain purposes, the degree of the catalytic activity is often less than would be desired. Combinations of platinum with other materials have also been proposed, primarily to further increase the activity of the platinum and to some degree to reduce the cost of the combination below that of platinum alone. For example, palladium has been used for the latter purpose, but the catalytic activity obtained still leaves room for improvements. In all of these catalyst materials, chemical and/or physical stability of the catalyst is also of importance in many applications. Thus a catalyst material which is easily dissolved or otherwise readily displaced, or which readily reacts chemically with other materials to form new compounds, or which readily breaks down into different materials, clearly is not desirable in many commercial applications.
The temperature at which the catalyst is effective is also important in many cases. Thus if the catalyst only becomes active at temperature above the lower end of the range in which it is intended to operate, or if it loses its activity or becomes physically or chemically unstable at temperatures including those at which it is intended to operate, it clearly will not be of most utility for its intended purpose.
One recently proposed catalyst is disclosed in my U.S. Pat. No. 3,511,714, issued May 12, 1970 and entitled "Chemical Source of Electrical Current, Catalyst Suitable for Use Therein and Method for the Manufacturing Thereof" which describes the use as a catalyst of various stoichiometric ordered alloys of certain noble metals, doped with minor amounts of certain metals for enhancing the electron-donating capabilities of the alloy. Such materials are useful, for example, at the electron-donating electrode of a fuel cell, but their performance is less than desired in applications where electron acceptance is the desired catalytic mechanism, as at the electron-accepting electrode of a fuel cell. Similarly, such materials are not as effective as desired for heterogeneous catalysis because their electron-accepting capabilities are not as great as would be desired for such purposes. Also, such materials are not as effective as is desirable in reducing certain pollutants such as oxides of nitrogen in engine exhaust.
In the article entitled "Rare Earth Oxides of Cobalt Rival Platinum in Treatment of Carbon Monoxide in Auto Exhausts", by Voorhoeve et al. and appearing in volume 177, page 353 of the 28 July 1972 periodical Science, various catalytic compounds are disclosed and compared with platinum for efficiency as catalysts in decreasing carbon monoxide in auto exhaust emissions. For example, Table 1 of the latter article shows results obtained with platinum catalysts in comparison with catalysts comprising various rare-earth oxides in the form of crushed single crystals.
Despite the very extensive work which has been done in the field of catalysts, for the purposes mentioned above and for other purposes, there still remains room for improvement with respect to catalytic activity, physical and chemical stability, and low price, and particularly so for catalysts to be used in reducing the pollutants in engine exhausts.
Accordingly it is an object of the invention to provide a new and useful catalyst material.
Another object is to provide such a catalyst which exhibits improved catalytic activity.
Another object is to provide such a catalyst which can be produced economically.
A further object is to provide a new catalyst for reducing nitrogen oxides and/or oxidizing carbon monoxide which is effective even at relatively low temperatures.
A further object is to provide a new catalyst of a high degree of effectiveness in converting oxides of nitrogen in engine exhausts to less harmful materials.
A further object is to provide a new catalyst which is effective in reducing the quantity of carbon monoxide in engine exhausts.
A further object is to provide a catalyst material having more than one component, the composition and proportions of which material can be adjusted during preparation to provide a desired operating temperature range for the catalyst, a suitable cost for the catalyst material, and a suitable degree of chemical and physical stability for the particular application.
It is also an object to provide a new method of making a catalyst material.
A further object is to provide a new catalyst suitable for use at one or more of the electrodes in a fuel cell.
Another object is to provide a new catalyst for catalytic cracking of petrochemicals.
Another object is to provide a new catalyst for facilitating synthesizing reactions between gaseous substances.
A further object is to provide a new catalyst suitable for catalyzing both oxidizing and reducing reactions for materials applied thereto.
It is also an object to provide new apparatus for reducing the pollutive emissions from engine exhaust.
Another object is to provide a new fuel cell and electrodes for use therein.
Another object is to provide a new catalyst effective as a substitute for platinum catalyst.